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Friday, October 28, 2011

Fukushima Daiichi update: October 28, 2011

A number of updates from Fukushima Daiichi...

-TEPCO has announced that as of today, the final additions to the enclosure structure at No. 1 reactor building have been made (air circulation and filtration equipment) and that the inspection of the structure and systems by NISA is completed satisfactorily. The structure itself has been completed for a while, but this might be considered as the official commissioning of the entire structure and ventilation system.

-TEPCO has also announced that it will drastically increase the amount of water being injected to No. 1 reactor in order to cut down on evaporation inside the structure. It appears that the high humidity environment is hampering the ability to work inside, so TEPCO will increase the feed rate through the feed line (normal feedwater injection line) upward from 4 cubic meters per hour to 7.5 cubic meters per hour over four days. When the conditions of the plant are ascertained at that point TEPCO will further increase water flow. This will also reduce drastically any gaseous emissions to the enclosure from the damaged reactor.

-TEPCO has discovered a nearly or else completely sheared axle shaft casing on the overhead crane at the common spent fuel building at Fukushima Daiichi. The cause is yet unknown, and no hazard is posed at this time.

-TEPCO is almost ready to place the gas handling system (improvised arrangement) at No. 2 reactor plant (to handle gases in the primary containment) into operation. This system will filter out radioactive airborne contaminants. Similar systems will be employed eventually at all three reactors.

-Finally, airborne releases from Fukushima Daiichi continue to decline .. contrary to many reports on anti-nuclear sites .. as shown by these two panels from a report issued by the Japanese Prime Minister's office.

4 comments:

@joffan: I'll have to dig around to see if they published that. This report is very recent, and comes right from the Office of the Prime Minister. NISA, JAIF or TEPCO might have the complete data... I'll look around. I think the reason the PM's office cut off there was because all the levels dropped below significance.

Surely the increased water injection reflects the desire to avoid turning the inside of the enclosure into a radioactive steam bath.However, afaik, the residual heat of the reactor 1 core is now down to about a megawatt. Assuming 1 calorie equals roughly 4 watt seconds, that is about 900 million calories/hr, dumped into 8 tons, about 8 million grams, of cooling water, well over 100 calories/gram. So the 8 tons/hr water injection appears insufficient to absorb the heat load without boiling. Presumably TEPCO estimates the residual heat to be less than 1 megawatt, but it still seems a marginal cooling flow rate. The continued poor performance of the water processing system, running at around 40% in the latest JAIF summary, may be constraining TEPCOs ability to cool more aggressively.

Will, certainly the second chart needs no extension but a rescaled time extension of the first set of graphs would be interesting. I know that the airborne levels have dropped to very low levels everywhere because the site boundary levels are extremely low (largely below detection), but an illustration of the progress towards that point would show the story nicely I think.